Is This Computer a Bot

My wife's computer's hard drive is continuously running/working regardless of whether nothing is being done on it. I'm worried that maybe it's been taken over as a Bot for malicious network activity. It has the latest version of Norton Internet Security fully updated, I've checked it using Malwarebytes, Advanced System Care and McAfee's Stinger but nothing is showing up. Has anyone any advice on any other check I can do for Bot type viruses/trojans etc.

If you're moderately experienced, and you're not running XP, then the Windows "Resource Monitor" would be a good place to start with tracking down the processes involved in causing all that disk activity - have a read here, and in particular, the "Disk" section.

Thanks for your response guys. I should have said that the computer is running XP. I've just run System Ninja, and excellent app for getting rid of all your junk files. It removed nearly 4000 files. It may be just coincidence but the computer is running much more quitely at the moment.